In an Ultra Violet (UV) reactor without any or adequate fluid control devices, i.e. a simple or plain chamber with UV source(s), the fluid takes the shortest path in its passage through the reactor between the inlet and outlet piping (see FIG. 1). Laminar flow based reactors require fluids with high transmission levels (low UV absorbance properties) to effect adequate dose levels on the fluid since the fluid in the region of the wall of the reactor (farthest away from the lamp or lamps) will receive the lowest dose from the UV source(s). The lower the transmission of the fluid (i.e. the higher the absorbance properties with respect to the UV wavelength), the lower the UV levels will be at the reactor wall, and with laminar (or short circuit) flow, the higher the biological reactor level breakthrough will be (i.e. higher levels of pathogens passing through the reactor untreated by the UV). From FIG. 1 it can be seen that the fluid on the opposite side of the inlet and outlet sections (A) are effectively stagnant (zero to no flow) and merely are a void of fluid when the reactor is initially filled with fluid—all (or most) of the fluid flow occurs between the inlet and outlet piping. Laminar flow based reactors have the advantage of lower head pressure requirements to drive fluid through them, but suffer from a small range of transmission level variance that they can effectively cope with or treat (i.e. suited to high UV transmittance water quality only). Laminar flow between the inlet and outlet of a reactor is therefore highly undesirable when the intent is to biologically treat fluids with a large range of transmission levels, and fluids with low or even very low UV transmission levels (UVT), approaching or down to 0% UVT.
Typical applications for low UVT fluid disinfection by UV radiation are found in the copper forming industry where an oil-water emulsion is used to cool and lubricate the copper forming process as it passes through the extrusion mold. The emulsion after forming is fed through a filter to remove any metallic debris. After the filter, the heated emulsion is fed though a heat exchanger to reduce the temperature and recycled back to the extrusion process. After the emulsion exits the heat exchanger and returns the extrusion mold its temperature is typically around 110° F. (43.3° C.), at this temperature bacteria and pathogens are able to consume the oil as nutrient. Microbial contamination of Metal Working Fluids (MWF's) causes biofouling and degradation and is also associated with several health hazards. Development of an effective control method is therefore essential to reduce microbial loading in MWF's. In order to demonstrate the harmful pathogenic potential to humans, some biological background of the species is necessary. Bacteria, Pseudomonas fluorescens, P. oleovorans subsp. lubricantis and Mycobacterium chelonae are found in the MWF's (Pseudomonas species). Stenotrophomonas maltophilia is an emerging multidrug-resistant global opportunistic pathogen found in the MWF's. The increasing incidence of nosocomial and community-acquired S. maltophilia infections is of particular concern for immunocompromised individuals, as this bacterial pathogen is associated with a significant fatality/case ratio. S. maltophilia is an environmental bacterium found in aqueous habitats, including plant rhizospheres, animals, foods, and water sources. Infections of S. maltophilia can occur in a range of organs and tissues; the organism is commonly found in respiratory tract infections. S. maltophilia has been reported to survive and persist in chlorinated water distribution systems. Treating the bacteria in the MWF's with chemicals (biocides) poses tremendous health issues to the factory workers, making them ill and adversely affecting production; not using biocides allows the pathogens to consume the oil in the MWF's which negatively affects the forming process and exposes the workers to a pathogen bio-hazard. The solution is to treat the pathogens with a non-chemical process such as UV radiation which protects both the oil in the MWF's and the factory personnel, however the UVT values of the MWF's can be as low as zero %; for this application a reactor with a high fluid mixing ratio, along with high levels of turbulence is required to effectively channel all the fluid within the reactor to the UV source as often, and for as long as possible. To achieve this objective the in-line mixer in this publication will be used.
Fruit juice and liquid dairy products require sterilization after production and prior to the packaging process (bottles, cartons etc); this can be achieved by an electron beam irradiating process which is a costly piece of equipment, or alternatively with a UV reactor with an in-line mixer. In the case of UV treatment of milk as opposed to traditional heat based pasteurization, the heat element is removed which therefore preserves the nutrients; the taste property is also preserved since the milk does not undergo a heating process with UV disinfection; heat alters the taste properties of milk. The higher the pasteurization level required, the higher the heat needs to be, and the more the taste is altered (long life milk is an example of high heat pasteurization). Both milk and orange juice have low to zero UVT properties and therefore require an ine-line based UV disinfection in order to achieve disinfection.
In the off-shore marine oil extraction process, sea water is often driven into the well to displace the oil; however this water requires disinfection otherwise the bio-loading of the sea water will consume the oil as nutrient; it can also cause bio-masses in the oil field which in turn then require higher water pressures to overcome them. A UV reactor with an in-line mixer will ensure maximum UV dose to the sea water with a range of UVT properties prior to the introduction into the well site.
Existing prior art apparatuses recognize the benefits of creating turbulence in the fluid under treatment with the purpose of thoroughly mixing it to assure that all the volume of the fluid under treatment will be subjected to UV radiation and to eliminate stagnant zones where the microorganisms are able to multiply while avoiding exposure to UV radiation. One invention (U.S. Pat. No. 5,626,768) proposes as method of creating turbulences to increase the fluid velocity, failing to realize that radiating all the fluid is only part of the disinfection process. Equally as important is the exposure time to UV radiation (UV dose); this exposure time needs to be long enough in order for the fluid under treatment to get the necessary dose of energy to deactivate the microorganisms' by way of damaging or destroying their DNA (dose dependant). Since the UV dose is proportional to both radiation intensity and exposure time, when increasing the fluid velocity, the exposure time decreases, with its undesirable consequences.
Other existing inventions use devices meant to create fluid turbulences, which upon careful examination do not deliver the claimed results. U.S. Pat. No. 5,675,153 includes a UV disinfection reactor which has a cylindrical shape and an internal helical deflector with radial slots. Liquid flow simulation studies on this apparatus shows that the claim is actually overstated. There is indeed some swirling effect which will result in turbulences, but it can be easily demonstrated using modern liquid flow simulation software that the ECO-UV invention is superior for opaque liquid treatment using UV radiation technology; furthermore ECO-UV's solution is far simpler and cheaper to manufacture. The same conclusion applies to U.S. Pat. No. 5,785,845 which develops an elaborate and complex internal profile of grooves and ridges to create a baffling structure that will alternate with ring-like and spiral-like paths in the contaminated liquid's path throughout an elongated reactor, or U.S. Pat. No. 6,280,615 B1 which develops an elaborate and complex internal profile of scallop shapes with peaks and troughs, with the peaks of the two surfaces being relatively offset so as to cause the liquid and the gas entering the chamber to flow along a generally sinuous path through the chamber to create a turbulent flow which promotes intimate mixing. Although the swirling effect will cause the fluid to spend additional time in the treatment zone, the turbulences created by this solution were found to have questionable efficiency.
Another invention (U.S. Pat. No. 6,344,176 B1) adopts a different approach in order to assure whole liquid volume exposure to UV radiation. It creates a thin film of the treated fluid by a partially immersing a rotating drum structure that will transport the fluid through an area with powerful UV radiation. The shortcomings associated with this invention are that it will need a large surface structure to efficiently treat adequate fluid flow, since it is only able to move a thin layer into the treatment zone. Turbulent flow is the only effective method for processing large volumes effectively; turbulence alone does not necessarily equate to desired pathogenic disinfection results; the method-specific control of turbulence with internal tangential flow patterns within the radiation zone is the required mechanism in order to optimize the disinfection performance of a reactor